Messages in this thread | | | Date | Fri, 6 Aug 2004 16:32:58 +0200 | From | Jens Axboe <> | Subject | Re: ide-cd problems |
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On Fri, Aug 06 2004, Alan Cox wrote: > On Gwe, 2004-08-06 at 07:23, Jens Axboe wrote: > > Perhaps if you acknowledge that it wont be perfect, then it's becomes > > more acceptable imo. So you can issue some commands that do write to the > > drive even as a regular user, but none that permanently alter the state > > of the drive or its media (to the best of our knowledge). Other commands > > you let through. > > The code you included is roughly the kind of filtering I mean except > that unknown commands must not get through without CAP_SYS_RAWIO. > Anything that is doubtful doesn't get through. As to the location you do > it there are at least two ways to handle that. One is that you stick the > CAP_SYS_RAWIO of the requester in a flag in the request block the other > is that you do it at the top layer. Some BSD socket implementations take > the former approach and it works very well as the driver can make a > final decision but is told the rights attached to the command. > > So once its > > switch() > { > case READ6: > case READ10: > ... > /* Always */ > break; > case WRITE6: > case WRITE10: > ... > /* if write */ > default: > if(capable(CAP_SYS_RAWIO)) > /* Only administrators get to do arbitary things */ > > I agree with it.
That's the case I don't agree with, and why I didn't like the idea originally. That suddenly requires a patching of the kernel because of new commands in new devices. Like when dvd readers became common, you can't just require people to update their kernel because a few new commands are needed to drive them from user space.
-- Jens Axboe
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